This is the most original and unique model of typewriter key I have ever came across with. It belongs to a Royal "Quiet de Luxe" and it is the only typewriter with this shape of key (D-shaped contour). This model was produced between 1939 and 1959 and designed to be more portable and to make less sound (pretty revolutionary for the times). It is extremely difficult to find this typewriter model so every piece is truly a treasure.
**Curious footnote: Ernest Hemingway wrote most of his novels in one of these.